As a connector for connecting a card board (a module board, a subsidiary board) of a graphic card and a main board (such as a mother board), a card edge connector is used. The card edge connector includes a contacting portion fitted to the card board and a terminal portion which has a shape of a surface mount (SMT) terminal or a through hole and is connected to the mother board.
However, the card edge connector does not have a part for absorbing an error in mounting position when each of the card board and the mother board is mounted to a housing or another board. Therefore, the card edge connector may be subjected to a mechanical load to be broken or the card board may be undesirably bent. This results in a problem that the mechanical load is also applied to various parts mounted on the card board and a solder at a mounting portion may possibly be separated or detached. In addition, the card board and the mother board must be moved up and down in a thickness direction.
As a connector for directly connecting a board and another board to each other, a double-ended card edge connector is proposed. The double-ended card edge connector comprises a housing having openings formed on opposite ends thereof, and a plurality of contacts to be connected to a plurality of conductive pads formed on opposite surfaces at an end portion of each of the boards (for example, see Japanese Unexamined Patent Application Publication (JP-A) No. H3-156872 and Japanese Unexamined Patent Application Publication (JP-A) No. 2000-12127).
However, the double-ended card edge connector described above does not have a structure for absorbing, by the connector itself, an error in positioning of a subsidiary board and a main board with respect to each other. Further, because of the structure of the connector, the subsidiary board and the main board must be different in position in the thickness direction. Furthermore, in case of the structure in which a contact of the card edge connector is fixed to a housing, the contact must be provided with a protruding portion formed between the contacting portion and the terminal portion and having a press-fit part to be fixed to the housing. Under the influence of the protruding portion, characteristic impedance is significantly lowered.
Furthermore, if a plurality of contacts are arranged at a narrow pitch, a distance between signal contacts becomes small. Therefore, characteristic impedance is inevitably lowered.
The contact of the card edge connector is different in shape between the contacting portion to be connected to the conductive pad of the card board and the terminal portion to be mounted to the mother board. Therefore, it is difficult to match the characteristic impedance because the impedance value is different between the case where a signal is supplied through the contacting portion to be connected to the card board and the case where a signal is supplied through the terminal portion to be mounted to the mother board.
In case of the narrow pitch, misalignment between the card board and the connector causes a significant problem. For example, the contacting portion of the contact may possibly be brought into contact not only with a corresponding conductive pad of the card board but also with a next adjacent pad to cause short-circuiting to occur.
Furthermore, in order to produce a highly-reliable product in view of limitation in pad width and a pitch error, a relatively wide pitch is required so that miniaturization is difficult.